SHACHI-PROBE: PVR2 Divergence Test ROM + Debug Overlay

Saved: 2026-02-23. This is the permanent copy. Build when ready.

Context

Flycast lies. We have 10 documented divergences (DIV-001 through DIV-010) between Flycast and TOTEM-1 hardware, plus 5 other DC emulators to evaluate (redream LLE, DEmul, MAME, Deecy, KAMUI.DLL). We need ground truth.

SHACHI-PROBE is a single KOS program with a menu. Each test isolates one divergence with a known-correct reference and a deliberately triggering case. Run on Flycast, redream, DEmul, burn to TOTEM-1 — compare screenshots. Result: accuracy matrix per emulator per divergence.

Additionally: a reusable debug overlay module (shachi_debug.h/c) that reads PVR2 registers live, modeled after Tower of Babel’s register viewer. This module ships inside SHACHI-PROBE but is designed to be dropped into any KOS project.